Linux Kernel up to 6.17.9 generic_hwtstamp_ioctl_lower null pointer dereference

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.17.9 and classified as critical. Affected by this vulnerability is the function generic_hwtstamp_ioctl_lower. Performing a manipulation results in null pointer dereference. This vulnerability was named CVE-2025-40255. There is no available exploit. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.17.9. This affects the function generic_hwtstamp_ioctl_lower. The manipulation with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower() The ethtool tsconfig Netlink path can trigger a null pointer dereference. A call chain such as: tsconfig_prepare_data() -> dev_get_hwtstamp_phylib() -> vlan_hwtstamp_get() -> generic_hwtstamp_get_lower() -> generic_hwtstamp_ioctl_lower() results in generic_hwtstamp_ioctl_lower() being called with kernel_cfg->ifr as NULL. The generic_hwtstamp_ioctl_lower() function does not expect a NULL ifr and dereferences it, leading to a system crash. Fix this by adding a NULL check for kernel_cfg->ifr in generic_hwtstamp_ioctl_lower(). If ifr is NULL, return -EINVAL.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2025-40255 since 04/16/2025. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 277518 (Linux Distros Unpatched Vulnerability : CVE-2025-40255), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.17.10 eliminates this vulnerability. Applying the patch 8817f816ae41908e9625c0770c4af0dcdcc01238/f796a8dec9beafcc0f6f0d3478ed685a15c5e062 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (277518) and CERT Bund (WID-SEC-2025-2747). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Debian Linux
• Google Cloud Platform
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• Open Source Linux Kernel
• RESF Rocky Linux
• Microsoft Azure Linux

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.17.0
• 6.17.1
• 6.17.2
• 6.17.3
• 6.17.4
• 6.17.5
• 6.17.6
• 6.17.7
• 6.17.8
• 6.17.9

License

• open-source

Website

• Vendor: https://www.kernel.org/

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